BTW I just opened up my modified intake manifold tonight and stock actually starts at 62mm from the factory. Will it help power to match it to 64-65mm? Probably, but at the same time if the TB itself is 64mm with a throttle shaft/plate running through the middle I would hazard a guess that it would flow about as good as a 62mm opening anyways, or at least be similar. A 64mm opening will definitely flow more than a 64mm TB with shaft through the center so I think the port matching will be in the under 5 whp category and hard to measure.

 

I'm sure it will help with the flow, I opened up my blitz manifold as well. If you are concern with 2mm in difference coming from the center shaft, go with the bigger Jun TB

 

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